Watershed land use is a primary driver of submersed aquatic plant community dynamics in the Upper Midwest

General understanding of submersed aquatic plant community responses to ecological change has been limited by data availability at broad scales. We used a 6,000 point intercept (PI) survey dataset to understand the lake- and watershed-level drivers of aquatic plant dynamics in Minnesota and Wisconsin (USA). We built annual taxonomic inventories from lakes with at least 10 years of PI data (41 lakes and 588 lake years from 2000-2022) and quantified community taxonomic richness, turnover rates, covariance, synchrony, directional compositional change, and stability over time. We fit structural equation models to investigate lake- and watershed-level drivers of these metrics. Models explained between 26% and 64% of the variation in each metric. We found that percent land cover that was agricultural or developed was the primary driver of community dynamics. Percent agricultural or developed cover was negatively related to taxonomic richness, was the primary driver of directional change in community composition and was negatively related to shifts in taxonomic rank abundance. It also influenced other lake-level drivers as it was negatively associated with water clarity and positively associated with invasion status. Lake area, shoreline development factor, and invasion status influenced at least one metric, while water clarity and the abundance of lakes, streams and wetlands in the watershed influenced none. The outsized importance of watershed land use is notable, suggesting that watershed-level management could benefit submersed taxonomic richness and community composition.

Primary Presenter: Jake Walsh, University of Minnesota-Twin Cities (jransom.walsh@gmail.com)

Authors:

Jake Walsh, University of Minnesota-Twin Cities  (walsh229@umn.edu)

Daniel Larkin, University of Minnesota-Twin Cities  (djlarkin@umn.edu)